Neuroanatomy Practice Questions

Q: What is true about the umbilical cord?

The right umbilical vein disappears. ### Explanation The umbilical cord is a vital structure connecting the fetus to the placenta. Understanding its embryological development and final anatomy is high-yield for NEET-PG. **1. Why Option C is Correct:** During early embryonic development, there are initially two umbilical veins (right and left). By the **6th to 7th week** of gestation, the **right umbilical vein undergoes atrophy and disappears**, leaving only the **left umbilical vein** to carry oxygenated blood from the placenta to the fetus. * *Mnemonic:* The **L**eft vein is the one that is **L**eft behind. **2. Analysis of Incorrect Options:** * **Option A & B:** A mature umbilical cord contains **two umbilical arteries** (carrying deoxygenated blood) and **one umbilical vein** (carrying oxygenated blood) [1], [2]. A "Single Umbilical Artery" (SUA) is a clinical abnormality often associated with congenital anomalies. * **Option D:** The average length of a full-term umbilical cord is approximately **50–60 cm**. A length below 30 cm is considered a "short cord," which can lead to complications like placental abruption or prolonged labor [1]. **3. Clinical Pearls & High-Yield Facts:** * **Wharton’s Jelly:** The mucoid connective tissue derived from extraembryonic mesoderm that protects the vessels from compression. * **Remnants:** The left umbilical vein becomes the **Ligamentum Teres** (in the free margin of the falciform ligament) [2], and the umbilical arteries become the **Medial Umbilical Ligaments**. * **Allantois:** The umbilical cord also contains the remnant of the allantois (which becomes the urachus/median umbilical ligament) [1]. * **False Knots:** These are simple redundant folds of the umbilical vessels and have no clinical significance, unlike true knots.

Q: The bulbocavernosus reflex is elicited by stimulation of which of the following?

Perianal skin. The **Bulbocavernosus Reflex (BCR)** is a polysynaptic reflex used to assess the integrity of the sacral spinal cord segments (**S2–S4**) and the pudendal nerve. [1] ### **Explanation of the Correct Answer** The reflex is elicited by stimulating the **perianal skin** (sensory input via the inferior rectal nerve, a branch of the pudendal nerve) or by squeezing the glans penis/clitoris. The positive response is the **contraction of the external anal sphincter**. In the context of this specific question, while multiple triggers exist, "Perianal skin" is a classic clinical maneuver to test the S4-S5 dermatomes and the integrity of the anal sphincter complex. ### **Analysis of Incorrect Options** * **A & B (Glans penis / Clitoris):** While squeezing the glans or clitoris *does* elicit the BCR, these are typically referred to as the "Glans-anal reflex." In many standardized examinations, if "Perianal skin" is provided as a distinct option, it specifically tests the cutaneous-anal contractile arc. * **C (Tugging of Foley catheter):** This is a common clinical method to elicit the reflex in patients with spinal cord injuries (by stimulating the stretch receptors in the bladder neck/prostatic urethra). However, it is a secondary clinical maneuver rather than the primary anatomical site for eliciting a superficial reflex. [1] ### **High-Yield Clinical Pearls for NEET-PG** * **Spinal Level:** S2, S3, S4 ("Keeps the poop off the floor"). * **Afferent & Efferent Limb:** Both are carried by the **Pudendal Nerve**. * **Clinical Significance:** The BCR is the **first reflex to return** after the resolution of **spinal shock**. [1] Its presence indicates that the injury is "Upper Motor Neuron" (suprasacral) rather than "Lower Motor Neuron" (sacral). * **Absence of Reflex:** If the reflex is absent after the acute phase of injury, it suggests an injury to the conus medullaris or cauda equina.

Q: Right homonymous hemianopia is caused by a lesion of which of the following?

Left optic radiation. ### Explanation **1. Why Left Optic Radiation is Correct:** Visual field defects follow a specific rule: a lesion **behind the optic chiasm** (retrochiasmal) results in a **contralateral homonymous hemianopia** [1]. The left optic radiation carries sensory information from the **right half of the visual field** of both eyes (specifically the temporal retina of the left eye and nasal retina of the right eye) [1]. Therefore, a lesion in the left optic radiation prevents visual signals from the right side of the world from reaching the primary visual cortex, resulting in a **Right Homonymous Hemianopia** [1]. **2. Analysis of Incorrect Options:** * **B. Right Geniculate Body:** A lesion here would cause a **Left** homonymous hemianopia because it is a retrochiasmal structure processing the contralateral (left) visual field [1]. * **C. Right Optic Nerve:** Lesions of the optic nerve occur **before** the chiasm [1]. This results in **ipsilateral monocular blindness** (total loss of vision in the right eye), not a hemianopia [1]. * **D. Right Optic Radiation:** Similar to the geniculate body, a lesion on the right side affects the opposite visual field, leading to a **Left** homonymous hemianopia [1]. **3. NEET-PG High-Yield Clinical Pearls:** * **Optic Chiasm Lesion:** Typically caused by pituitary adenomas; results in **Bitemporal Hemianopia** (loss of peripheral vision) [1]. * **Meyer’s Loop (Temporal Lobe):** Part of the optic radiation; a lesion here causes "Pie in the sky" (**Superior Quadrantanopia**). * **Baum’s Loop (Parietal Lobe):** Part of the optic radiation; a lesion here causes "Pie on the floor" (**Inferior Quadrantanopia**). * **Macular Sparing:** Often seen in PCA (Posterior Cerebral Artery) strokes affecting the visual cortex because the macula has a dual blood supply (PCA and MCA) [1].

Q: Which of the following statements about apoptosis is true?

Councilman bodies are associated with apoptosis. **Explanation:** **Apoptosis** is a process of programmed cell death characterized by specific morphological changes without the leakage of cellular contents. **Why Option C is correct:** **Councilman bodies** (also known as acidophilic bodies) are eosinophilic, rounded remnants of apoptotic hepatocytes. They are classically seen in **Viral Hepatitis** (especially Yellow Fever and Hepatitis B/C). During apoptosis, the cell shrinks and the chromatin condenses (pyknosis) followed by fragmentation (karyorrhexis), eventually forming membrane-bound **apoptotic bodies** that are phagocytosed. **Why other options are incorrect:** * **Option A (Hypoxia):** Hypoxia typically leads to **Necrosis** (specifically coagulative necrosis), which is an accidental, energy-independent form of cell death resulting from severe injury. * **Option B (Inflammatory reaction):** A hallmark of apoptosis is the **absence of inflammation**. Because the cell membrane remains intact and apoptotic bodies are rapidly cleared by macrophages, no intracellular contents leak out to trigger an inflammatory response. In contrast, necrosis always incites inflammation. * **Option D (Cell membrane damage):** In apoptosis, the **cell membrane remains intact** but undergoes structural alterations (like the movement of phosphatidylserine to the outer leaflet) to signal phagocytes. Loss of membrane integrity is a defining feature of necrosis. [1] **High-Yield NEET-PG Pearls:** * **Key Morphological Feature:** Cell shrinkage (not swelling). * **Molecular Marker:** Caspases (Cysteine proteases) are the executioners of apoptosis. * **DNA Pattern:** "Step-ladder" pattern on gel electrophoresis (due to internucleosomal cleavage by endonucleases) [1]. * **Anti-apoptotic gene:** Bcl-2; **Pro-apoptotic genes:** Bax and Bak.

Q: Testes completely descend into the scrotum by which month of intrauterine life?

End of the 9th month of intrauterine life. ### Explanation The descent of the testes is a complex physiological process guided by hormonal (Androgens, MIS) and mechanical factors (Gubernaculum). It occurs in two distinct phases: 1. **Trans-abdominal phase:** The testes reach the deep inguinal ring by the **3rd month** of intrauterine life (IUL). 2. **Trans-inguinal phase:** The testes remain at the deep inguinal ring from the 3rd to the 7th month. They then traverse the inguinal canal during the **7th month**. 3. **Scrotal entry:** The testes reach the superficial inguinal ring by the **8th month** and finally reach the bottom of the **scrotum by the end of the 9th month** (just before birth). #### Analysis of Options: * **Option A (7th Month):** At this stage, the testes are typically passing through the inguinal canal. * **Option B (8th Month):** At this stage, the testes have reached the superficial inguinal ring but have not yet fully descended to the base of the scrotum. * **Option C (9th Month):** **Correct.** Full descent into the scrotum is completed just prior to birth in a full-term neonate. * **Option D (After Birth):** While descent can occasionally complete postnatally in preterm infants, it is considered a developmental delay (Cryptorchidism) if not present at birth in full-term infants. #### High-Yield Clinical Pearls: * **Cryptorchidism:** Failure of the testes to descend. The most common site of an undescended testis is the **inguinal canal**. * **Ectopic Testis:** Testis deviated from the normal path of descent (most common site: **Superficial inguinal pouch**). * **Gubernaculum:** The mesenchymal structure that guides the descent. Its remnant in adults is the **scrotal ligament**. * **Processus Vaginalis:** An outpocketing of peritoneum that precedes the testis; failure of this to obliterate leads to **Congenital Inguinal Hernia** or **Hydrocele**.

Q: Duchenne dystrophy is a

X-linked recessive disease. **Explanation:** Duchenne Muscular Dystrophy (DMD) is a severe, progressive neuromuscular disorder caused by a mutation in the **DMD gene** located on the **short arm of the X chromosome (Xp21)**. 1. **Why D is correct:** DMD follows an **X-linked recessive** inheritance pattern. Because the gene is on the X chromosome, males (XY) who inherit the defective gene will manifest the disease. Females (XX) are typically asymptomatic carriers unless they have skewed X-inactivation (Lyonization) or Turner syndrome. The mutation leads to a complete absence of **dystrophin**, a protein essential for maintaining the structural integrity of the muscle cell membrane (sarcolemma) [1]. 2. **Why other options are incorrect:** * **A & C (Autosomal):** The DMD gene is located on a sex chromosome (X), not an autosome. Autosomal muscular dystrophies include Limb-Girdle Muscular Dystrophy [2]. * **B (X-linked Dominant):** In dominant inheritance, females would be equally affected. DMD primarily affects males, which is the hallmark of recessive X-linked traits. **High-Yield Clinical Pearls for NEET-PG:** * **Gower’s Sign:** The child uses their hands to "climb up" their own legs to stand, indicating proximal muscle weakness (specifically gluteus maximus). * **Pseudohypertrophy:** The calves appear large but are actually composed of fat and connective tissue replacing lost muscle. * **Diagnosis:** Elevated **Serum Creatine Kinase (CK)** levels (often 10–100x normal). Gold standard is genetic testing; muscle biopsy shows absent dystrophin [1]. * **Becker Muscular Dystrophy:** A milder form caused by *truncated* (rather than absent) dystrophin, also X-linked recessive [1].

Q: The double aorta develops from which structure?

Right dorsal aorta. ### Explanation **Concept:** In normal embryonic development, the **right dorsal aorta** regresses between the origin of the 7th intersegmental artery and its junction with the left dorsal aorta. If this regression fails to occur, the right dorsal aorta persists, resulting in a **Double Aortic Arch**. This vascular ring encircles the trachea and esophagus, often leading to clinical symptoms like stridor or dysphagia [1]. **Analysis of Options:** * **Right dorsal aorta (Correct):** Its persistence, along with the normal left dorsal aorta, creates a complete vascular ring [1]. This is the embryological basis for a double aorta. * **1st branchial arch artery:** This normally disappears almost completely, leaving behind only a small portion that forms the **maxillary artery**. * **2nd branchial arch artery:** The dorsal part of this artery persists to form the **stapedial artery** and the **hyoid artery**; it does not contribute to the aortic arch. * **Left dorsal aorta:** This is a normal component of the definitive descending aorta. Its presence is physiological; only the abnormal persistence of its right-sided counterpart leads to the "double" pathology. **High-Yield Facts for NEET-PG:** * **3rd Arch:** Forms the Common Carotid and proximal Internal Carotid arteries. * **4th Arch:** Left side forms the **Arch of Aorta**; Right side forms the proximal **Right Subclavian artery**. * **6th Arch (Pulmonary Arch):** Left side forms the Left Pulmonary artery and **Ductus Arteriosus**; Right side forms the Right Pulmonary artery. * **Clinical Pearl:** A double aortic arch is the most common symptomatic vascular ring [1]. It presents as "Dysphagia Lusoria" (difficulty swallowing) or respiratory distress in infants [2].

Question 1

What is true about the umbilical cord?

Accepted Answer

The right umbilical vein disappears

Answer

Contains 2 umbilical veins

Answer

Contains 1 umbilical artery

Answer

Length is 25-30 cm

Question 2

The bulbocavernosus reflex is elicited by stimulation of which of the following?

Accepted Answer

Perianal skin

Answer

Glans penis

Answer

Clitoris

Answer

Tugging of Foley catheter

Question 3

In the embryonic period, all of the following are true EXCEPT?

Accepted Answer

Formation of mesoderm by 6 weeks

Answer

Formation of the blastocyst by 8 days

Answer

Formation of ectoderm and endoderm by 2 weeks

Answer

Formation of a human-like embryo by 4 weeks

Question 4

Right homonymous hemianopia is caused by a lesion of which of the following?

Accepted Answer

Left optic radiation

Answer

Right geniculate body

Answer

Right optic nerve

Answer

Right optic radiation

Question 5

Which of the following statements about apoptosis is true?

Accepted Answer

Councilman bodies are associated with apoptosis

Answer

Injury due to hypoxia

Answer

Inflammatory reaction is present

Answer

Cell membrane is damaged

Question 6

Testes completely descend into the scrotum by which month of intrauterine life?

Accepted Answer

End of the 9th month of intrauterine life

Answer

End of the 7th month of intrauterine life

Answer

End of the 8th month of intrauterine life

Answer

After birth

Question 7

A cell membrane is damaged by a needle. How does the repair occur?

Accepted Answer

Resealing by the lipid bilayer

Answer

Lateral movements of proteins

Answer

Enzymatic reactions

Answer

Calcium facilitated by membrane repair

Question 8

Duchenne dystrophy is a

Accepted Answer

X-linked recessive disease

Answer

Autosomal dominant disorder

Answer

X-linked dominant disease

Answer

Autosomal recessive disease

Question 9

Which of the following is both mutagenic and morphogenic?

Accepted Answer

IGF1

Answer

FGF

Answer

PDGF

Answer

Bone morphogenic protein

Question 10

The double aorta develops from which structure?

Accepted Answer

Right dorsal aorta

Answer

1st branchial arch artery

Answer

2nd branchial arch artery

Answer

Left dorsal aorta

Neuroanatomy — MCQs

Neuroanatomy — MCQs

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